It has been shown that intravascular stents are an excellent means to maintain the patency of blood vessels following balloon angioplasty. Palmaz in U.S. Pat. No. 4,733,665 describes a balloon expandable slotted tube stent. This and other designs currently known in the art would have fairly uniform stent rigidity except at the ends where the stent is typically weaker.
The weakness at the end can cause over expansion of the end struts, which can increase injury to the vessel wall. The more the injury, the greater the neointimal hyperplasia and the probability of reclosing of the stent within 6 months following implantation.
Ostial obstructions such as those that often occur at the junction of the aorta and renal artery are difficult to treat with standard angioplasty balloons or stents. Ostial lesions tend to exhibit extreme elastic recoil which makes balloon angioplasty ineffective. Enhanced end strength would be of great value for treating ostial lesions.
On the other hand, calcified obstructions may require enhanced rigidity in the center section of the stent.